Current air inlets for turbochargers have a tube with a filter at the upstream end and a downstream end connected to the turbocharger for a motor vehicle engine. If the air inlet tube is curved just before the turbocharger a low pressure area can be created along the inside of the bend just before the turbocharger. A hose may connect this low pressure location on the air inlet to a crankcase in order to draw fumes from the crankcase through the tube and into the air inlet tube so the fumes may be burned in the engine. The pressure at the location where the hose outlet connects to the air inlet tube has to be lower than the pressure inside the crankcase in order to draw crankcase fumes into the air inlet and engine. The pressure in the hose or at the connection of the hose and the air inlet is monitored and if the pressure falls outside of specified parameters an engine control module will store a diagnostic trouble code and a check engine light may be lit.
Prior art designs place a movable venturi plug inside the air inlet tube and move the venturi plug along the axis of the inlet tube to vary the flow through the tube and indirectly to vary the vacuum on the opening of the crankcase hose adjacent the venturi plug. Such a design is described in U.S. Pat. No. 7,886,727 to Ulrey. But the venturi plug blocks a significant portion of the air inlet tube at the center of that tube, resulting in an undesirable pressure drop along the length of the inlet tube. It is desirable to minimize the pressure drop along the inlet tube in order to increase the volume of flow through the inlet tube and turbocharger. If the variable venturi is replaced with a typical open throat venturi the cross-sectional area reduction and flow restriction are still undesirable and the venturi flow is affected by the opening of the crankcase hose at or adjacent to the venturi. There is thus a need for an improved way to maintain the pressure or suction at the juncture of the crankcase hose and air inlet tube while achieving a low pressure drop in the air inlet tube.
Prior art designs also placed a venturi in the crankcase ventilation hose in order to draw vapors from the crankcase to the engine, as in published application US 2014/0014080 to Beshay. But such designs require a complex crankcase ventilation hose, require complex controls for the venturi and are still subject to pressure variations in the air inlet tube to ensure sufficient pressure drop across the venturi in the crankcase hose to operate correctly. There is thus a need for an improved and simpler way to maintain the pressure at the juncture of the crankcase hose with and air inlet tube.